Rotating Cap Mechanism for Ink Jet Print Head Nozzle Protection
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Solution Overview
Problem
Drop-on-demand ink jet printers face challenges in preventing ink nozzle drying in industrial settings due to the rapid evaporation of solvents, making it impractical to move the print head to a capping station, especially in tight spaces or high-speed industrial environments.
Innovation Solution
A capping member for the print head that rotates about an axis transverse to the print face, driven by cam surfaces, which moves between open and closed positions to cap the nozzles without obstructing the printing path, ensuring the nozzles are sealed without sliding contact and accommodating the movement of products on a conveyor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capping station is used to prevent nozzle drying, then nozzle reliability is improved, but device complexity and space requirements increase
Solution Approach 1:
The capping member is integrated into the print head assembly itself, with the cap nested within the print head housing and the cam mechanism embedded in the print head body. This eliminates the need for a separate external capping station, reducing overall device complexity while maintaining nozzle protection functionality.
Solution Approach 2:
The capping function is merged with the print head structure by integrating the capping member, cam surfaces, and driving mechanism into a single compact assembly. This combination allows the print head to perform both printing and capping operations without requiring separate dedicated capping equipment.
2Reliability
If the print head is moved to a capping station, then nozzle drying is prevented, but productivity decreases due to movement time
Solution Approach 1:
The capping member remains positioned within the print head assembly during printing operations, ready to close immediately when printing stops. This preliminary positioning eliminates the need to move the print head to a separate capping station, allowing instant capping action that maintains high printing productivity while preventing nozzle drying.
3Reliability
If a protective cap is mounted on the print cartridge, then nozzle protection is improved, but the cap may interfere with printing operation
Solution Approach 1:
The capping member is designed to be dynamically positionable within the print head assembly, moving between an open position during printing that does not interfere with nozzle operation and a closed position when printing stops to protect the nozzles. This dynamic positioning is achieved through the cam mechanism that allows the cap to rotate and adjust its position as needed.
4Reliability
If the capping member rotates about an axis transverse to the print face, then nozzle sealing is improved without obstructing printing path, but mechanism complexity increases
Solution Approach 1:
The capping member is designed with an asymmetric rotation axis that is transverse to the print face rather than parallel to it. This asymmetric orientation allows the cap to rotate in a manner that brings the sealing surface into contact with the nozzles effectively while keeping the bulk of the capping member clear of the printing path during operation.
Solution Approach 2:
By changing the rotation axis from a conventional parallel orientation to a transverse orientation perpendicular to the print face, the invention utilizes a different spatial dimension for the capping motion. This dimensional change allows the sealing action to occur without the capping member obstructing the printing path in the original operational plane.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively prevents ink nozzle drying by maintaining a seal around the nozzles during non-printing periods without interfering with the printing process, even in high-speed industrial settings, ensuring reliable operation and maintaining print quality.
Implementation Method 1
an arrangement of cams to drive the capping member along the axis of rotation by interaction of opposing cam surfaces during at least part of its rotation between the open and closed positions
Implementation Method 2
The solvent or solvents in the ink used in ink jet printers tends to evaporate quickly... there is a tendency for the solvent to evaporate through the print head nozzle or nozzles
Data Source
Figure 1~3C
Figure 4~5
Figure 6~7
AI summary
A cap 13, 15, for the print face 9 of a drop-on-demand ink jet printer moves between a closed position, in which it covers the print nozzles on the print face 9, and an open position in which the print nozzles are uncovered, without requiring movement of the print face 9. In the open position, the cap is recessed relative to the front surface 21 of the printhead. For at least part of the movement of the cap, it is further forward than the print face 9, so that it does not slide across and damage the print nozzles. The drop-on-demand ink jet printer may be used to print onto objects 3 conveyed past it, for example on a packing line. The cap 13, 15, does not obstruct the path of the objects 3 even if they pass very close (e.g. 0.5 mm) to the print face 9 because its uncapped position is further back than the front surface 21 of the printhead.